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I−APPLICATION
15CHAX 2 through 5 ton (7.0 through 17.6kW) model units
are single phase air conditioning units designed for outdoor
installation on a slab or roof top.The units are available in two
cabinet sizes. Electric heat can be factory or field installed if
required. Refer to the Engineering Handbook for more spe-
cific application data.
II−UNIT COMPONENTS
15CHAX components are shown in figure 1. Control box com-
ponents are shown in figure 2.
A−Control Box Components
1−Compressor Contactor K1
K1 is a 24VAC to line voltage s ingle pole double break contac-
tor, which energizes the compressor in response to thermostat
demand.
2−Control Transformer T1
All 15CHAX series units use line voltage to 24VAC transformer
mounted in the control box. The transformer supplies power to
control circuits in the unit. Transformers use two primary volt-
age taps as shown in figure 3.
FIGURE 3
240 VOLTS
208 VOLTS
PRIMARY
SECONDARY
208 / 240 VOLT TRANSFORMER
24 VOLTS
L1
L2
3−Dual Capacitor C12
The compressor and condenser fan in the 15CHAX series
units use permanent split capacitor motors. The capacitor is lo-
cated in the control box. A dual rated capacitor is used for both
the condenser fan motor and the compressor (see unit wiring
diagram per respective unit). The fan side and the compressor
side of the capacitor have different MFD ratings. See side of
capacitor for ratings.
4− Blower Control A15
Electric shock hazard. Can cause injury or
death. Before attempting to perform any
service or maintenance, turn the electrical
power to unit OFF at disconnect switch(es).
Unit may have multiple power supplies.
WARNING
!
15CHAX units are equipped with a variable speed motor
that is capable of maintaining a specified CFM throughout
the external static range. A particular CFM can be obtained
by positioning jumpers (
COOL
,
HEAT
, and
ADJUST
) on
the blower control board. The HEAT and COOL jumpers
are labeled A, B, C and D. Each of the numbers corre-
sponds with an air volume (CFM) setting. The
ADJUST
jumper is labeled Test, −, +, and Norm. The + and − pin set-
tings are used to add or subtract a percentage of the CFM
selected. The Test jumper is used to operate the motor in
the test mode. See figure 4.
Factory settings for the blower speed jumpers are given in
the wiring diagram. Figure 4 shows the blower control
board. Use tables 1, 2 and 3 to determine the correct air vol-
ume for operation in heat and cool mode.
The CFM
LED located on the blower control board flashes
one time per 100 cfm to indicate selected blower speed.
For example, if the unit is operating at 1000 CFM,
CFM
LED
will flash 10 times. If the CFM is 1150,
CFM
LED will flash 11
full times plus one fast or half flash.
At times the light may appear to flicker or glow. This takes
place when the control is communicating with the motor be-
tween cycles. This is normal operation.
Read through the jumper settings section before adjusting
the jumper to obtain the appropriate blower speed.
To change jumper positions, gently pull the jumper off the pins
and place it on the desired set of pins. The following section
outlines the different jumper selections available and condi-
tions associated with each one. Refer to figure 4.
After the CFM for each application has been determined,
the jumper settings must be adjusted to reflect those given
in tables 1, 2 and 3. From the tables, determine which row
most closely matches the desired CFM. Once a specific row
has been chosen (+, NORMAL, or −), CFM volumes from
other rows cannot be used. Below are descriptions of the
jumper selections.
The variable speed motor slowly ramps up to and down
from the selected air flow during both cooling and heating
demand. This minimizes noise and eliminates the initial
blast of air when the blower is initially energized.
ADJUST
The
ADJUST
pins allow the motor to run at normal speed,
approximately 15 percent higher, or approximately 15 per-
cent lower than normal speed. Tables 1, 2 and 3 give three
rows (+, NORMAL, and −) with their respective CFM vol-
umes. Notice that the normal adjustment setting for cool
speed position D in table 1 is 900 CFM. The + adjustment
setting for that position is 1035 CFM and for the − adjust-
ment setting is 765 CFM. After the adjustment setting has
been determined, choose the remaining speed settings
from those offered in the table in that row.
The TEST pin is available to bypass the blower control and
run the motor at approximately 70 percent to make sure that
the motor is operational. This is used mainly in trouble-
shooting. The G terminal must be energized for the motor to
run.
